Creating a restore copy from a copy of source data in a repository having source data at different point-in-times and reading data from the repository for the restore copy

ABSTRACT

Provided are a computer program product, system, and method for creating a restore copy from a copy of source data in a repository having source data at different point-in-times and reading data from the repository for the restore copy. The source data is copied as of an initial point-in-time to a repository. Point-in-time copies at different point-in-times of the source data are initiated following the initial point-in-time. Change information for the point-in-time copy indicating changed data in the source data that changed between the point-in-time of the point-in-time copy and a subsequent point-in-time are transmitted to the repository. For each point-in-time copy, changed source data indicated in the change information for the point-in-time copy as changed is copied to the repository. A restore copy is returned to a restore request before the source data in the repository as of a restore point-in-time is copied to the restore copy.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a computer program product, system, and method for creating a restore copy from a copy of source data in a repository having source data at different point-in-times and reading data from the repository for the restore copy.

2. Description of the Related Art

In a storage environment, a storage controller may create point-in-time (“PiT”) copies of a production volume using point-in-time copy techniques, such as the IBM FlashCopy® (FlashCopy is a registered trademark of IBM), snapshot, etc. A point-in-time copy replicates data in a manner that appears instantaneous and allows a host to continue accessing the source volume while actual data transfers to the copy volume are deferred to a later time. The PiT copy appears instantaneous because complete is returned to the copy operation in response to generating the relationship data structures without copying the data from the source to the target volumes. PiT copy techniques typically defer the transfer of the data in the source volume at the time the PiT copy relationship was established to the copy target volume until a write operation is requested to that data block on the source volume. Data transfers may also proceed as a background copy process with minimal impact on system performance. The PiT copy relationships that are immediately established in response to the PiT copy command include a bitmap or other data structure indicating the location of blocks in the volume at either the source volume or the copy volume. The PiT copy comprises the combination of the data in the source volume and the data to be overwritten by the updates transferred to the target volume.

When an update to a block in the source volume involved in a PiT copy relationship is received, the copy of the track as of the point-in-time must be copied to side file or the target volume before the new data for the track is written to the source volume, overwriting the point-in-time copy of the data.

SUMMARY

Provided are a computer program product, system, and method for creating a restore copy from a copy of source data in a repository having source data at different point-in-times and reading data from the repository for the restore copy. The source data is copied as of an initial point-in-time to a repository. Point-in-time copies at different point-in-times of the source data are initiated following the initial point-in-time. In response to completing each of the point-in-time copies, transmitting to the repository change information for the point-in-time copy indicating changed data in the source data that changed between the point-in-time of the point-in-time copy and a subsequent point-in-time. For each point-in-time copy, copying changed source data comprising source data indicated in the change information for the point-in-time copy as changed to the repository. Receiving a restore request to restore the source data as of a restore point-in-time. The restore copy is returned to the restore request before the source data in the repository as of the restore point-in-time is copied to the restore copy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a storage environment.

FIG. 2 illustrates an embodiment of storage controller point-in-time copy information.

FIG. 3 illustrates an embodiment of repository point-in-time copy information.

FIG. 4 illustrates an embodiment of operations to create a repository having source data at different point-in-times.

FIGS. 5 a, 5 b, and 5 c illustrate examples of states of the source data and the repository at different point-in-times.

FIG. 6 illustrates an embodiment of operations to create a restore copy.

FIG. 7 illustrates an embodiment of restore copy information.

FIG. 8 illustrates an embodiment of data unit information in the restore copy information for each data unit in the restore copy.

FIG. 9 illustrates an embodiment of operations to generate restore copy information.

FIG. 10 illustrates an embodiment of operations to process a write request to a restore copy.

FIG. 11 illustrates an embodiment of operations to process a read request to the restore copy.

FIG. 12 illustrates an embodiment of a storage environment including virtual machines.

FIG. 13 illustrates a computing environment in which the components of FIGS. 1 and 12 may be implemented.

DETAILED DESCRIPTION

Described embodiments provide techniques for creating a repository to maintain a full copy of the source data and point-in-time copies of the source data to allow the source data to be restored from the repository at different point-in-times. Further, with described embodiments, the operations to maintain the point-in-time (“PiT”) copy information in the repository and perform the restore operations may be performed by a program component separate from the storage controller logic creating the PiT copies from the source data, so that the repository is separately maintained, used, and managed from the storage controller. Yet further, with described embodiments, a restore copy may be created and data requests to the data units in the restore copy may be returned from the repository to return data units as of a restore point-in-time of the restore copy.

FIG. 1 illustrates an embodiment of a data storage environment having a storage controller 100 managing access to a first storage 102 that includes source data 104, such as a production volume used by different host systems. A host 106 includes a repository copy manager program 108 to manage the copying of the source data 104 to a repository 110 in a second storage 112. The storage controller 100, host 106, and second storage 112 may communicate over a network 114.

The storage controller 100 includes a point-in-time (“PiT”) copy manager 116 to create point-in-time copies of the source data 104, e.g., FlashCopy, snapshot, etc. When creating a PiT copy, the PiT copy manager 116 generates PiT copy information 200 on the PiT copy created as of a point-in-time. The storage controller 100 further includes an operating system 118, including the code and logic to manage Input/Output (“I/O”) requests to the source data 104. The operating system 118 may configure the source data 104 in one or more volumes and data is stored in data units, such as tracks, logical block addresses (LBAs), extents, etc. The PiT copy manager 116 may be a copy service supplied with the operating system 118.

The storages 102 and 112 may store tracks in a Redundant Array of Independent Disks (RAID) configuration where strides of tracks are written across multiple storage devices comprising the storages 102 and 112. The storages 102 and 112 may each comprise one or more storage devices known in the art, such as interconnected storage devices, where the storage devices may comprise hard disk drives, solid state storage device (SSD) comprised of solid state electronics, such as a EEPROM (Electrically Erasable Programmable Read-Only Memory), flash memory, flash disk, Random Access Memory (RAM) drive, storage-class memory (SCM), etc., magnetic storage disk, optical disk, tape, etc.

The network 114 may comprise a network such as one or more interconnected Local Area Networks (LAN), Storage Area Networks (SAN), Wide Area Network (WAN), peer-to-peer network, wireless network, etc.

The PiT copy manager 116 performs a PiT copy operation that replicates data in a manner that appears instantaneous and allows a process to continue accessing the source volume while actual data transfers to the copy volume are deferred to a later time. The PiT copy appears instantaneous because complete is returned to the copy operation in response to generating the relationship data structures without copying the data.

The repository copy manager 108 copies changed data of the source data 104 at different point-in-times to changed data 120 in the repository 110, including an initial copy of all the source data, and copies the PiT copy information 200 at the storage controller 100 to the repository 110 to store as repository PiT copy information 300 in the repository 110. The repository copy manager 108 uses the PiT copy information 300 to determine changed data at the source data 104 to copy to the changed data 120. To copy all the source data as of an initial point-in-time to the repository 110, the repository copy manager 108 may modify the change information for the initial PiT copy, or PiT bitmap, having a bit for each data unit in the source data 104 to indicate that all the source data has changed to generate modified initial change information 200 ₀′ that indicates that each data unit in the source data 104 has changed. The repository copy manager 108 may then copy all the source data 104 units in the modified initial change information 200 ₀′ to the changed data 120 in the repository 110 to provide a full copy of the source data 104 as of the initial point-in-time (T₀) in the repository. The repository copy manager 108 would use the change information in PiT copy information 200 for PiT copies following the initial point-in-time to copy changed data at different point-in-times to the changed data 120 in the repository 110.

With described embodiments, the repository copy manager 108 maintains a separate full copy of the source data 104 and the PiT copy information 300 of the source data 104 in a separate storage 112 so that data can be restored to different point-in-times independently of the source data 104 in the first storage 102 and the PiT copy information 200 a at the storage controller 100. Thus, the repository 110 by allowing for independent restore of the source data 104 provides a secure backup independent to protect from failure at the storage controller 100 or first storage 102.

In certain embodiments, the creation and management of the repository 110 is managed by a repository copy manager 108 that is separate from the storage controller 100 programs, such as the PiT copy manager 116 that creates the PiT copies.

The host 106 may further include a restore copy I/O manager 126 to manage I/O requests directed to restore copies 124 to ensure that data as of a restore time for which the restore copy 124 is create is returned from the restore copy 124 or the repository 110.

To generate the restore copy 124, the repository copy manager 108 may utilize restore copy information 130 indicating the source data in the changed data 120 that needs to be copied to the restore copy 124.

In the embodiment of FIG. 1, the repository creation and restore operations may be performed by program components, such as the repository copy manager 108 and the restore copy I/O manager 126, that are separate from the storage controller logic, e.g., the PiT copy manager 116 that created the PiT copies. In an alternative embodiment, the repository copy manager 108, the repository copy I/O manager 126, and/or the repository 110 may be maintained on the storage controller 100.

FIG. 2 illustrates an instance of the PiT copy information 200, for PiT copy at time T_(i), which may comprise information maintained for the storage controller PiT copy information 200, and may include a PiT copy identifier 202 identifying the PiT copy created by the PiT copy manager 116 at the storage controller 100; a point-in-time 204 of the PiT copy 202, which may mean that data is consistent as of that point-in-time 204; change information 206 indicating which data or tracks in the source data 104 has changed since the point-in-time 204 and while the PiT copy 202 was open, which may comprise a bitmap having a bit for each data unit (e.g., track) that is set to one of two values indicating the data or track represented by the bit has or has not been updated since the point-in-time 204; and indicate the changed PiT data 208 comprising the data at the point-in-time 204 that was changed after the point-in-time 204 while the PiT copy 202 was open and still being updated. PiT copy information may be maintained for an initial PiT copy taken at the initial time T₀ and for subsequent PiT copies taken at subsequent point-in-times.

In one embodiment, the PiT copy may be completed or frozen at a time subsequent to the point-in-time 204, such that the changed PiT data 208 includes data changed from the point-in-time 204 until the PiT copy 202 was completed, e.g., frozen or a new PiT copy initiated, and does not include changed data after the PiT copy 202 was completed, e.g., frozen. A PiT copy 202 may be completed upon a freeze command or initiating a subsequent PiT copy at a subsequent point-in-time to the point-in-time 204. A completed PiT copy 202 may be consistent as of the point-in-time. Other techniques may be used to complete, e.g., freeze, the PiT copy.

FIG. 3 illustrates an embodiment of an instance of PiT copy information 300, maintained in the repository 110, that is generated from an instance of PiT copy information 200, from the storage controller 100, and includes a PiT copy identifier 302 identifying the PiT copy 202 created by the PiT copy manager 116 at the storage controller 100; a point-in-time 304 of the PiT copy 302, which may mean that data is consistent as of that point-in-time 304; change information 306 indicating which data or tracks in the source data 104 has changed since the point-in-time 304 and while the PiT copy 302 was open, which may comprise a bitmap; and a repository offset 308 indicating an offset in the changed data 120 at which the data indicated in the change information 306 for the PiT copy 302 is located. The location in the changed data 120 of a particular changed data unit for a PiT copy 302 can be determined at an offset from the repository offset 208 in the changed data 120, such as by summing the repository offset 208 with the number of the changed unit indicated in the change information 306, i.e., the jth data unit, times a length of the data unit. In this way, changed data from a PiT copy 300 are written sequentially after the last written data in the change data 120 in the repository 110.

FIG. 4 illustrates an embodiment of operations performed by the repository copy manager 108 and the PiT copy manager 116 to copy the source data 104 to the repository 110 at different points-in-time from the PiT copies for the source data 104, such as a production volume, created by the PiT copy manager 116. Upon initiating (at block 400) repository copy operations for source data 104, the repository copy manager 108 sends (at block 402) a command to the PiT copy manager 116 to create an initial PiT copy 200 ₀ at an initial point-in-time, referred to herein as T₀. The repository copy manager 108 may modify the initial change information 200 ₀ to generate modified initial change 200 ₀′ indicating that all source data units in the source data have changed. The repository copy manager 108 may send (at block 406) to the repository 110 the modified initial change information 200 ₀′, which indicates that all data units have changed and the changed PiT data 208 ₀ for the initial PiT copy (T₀) indicated in the modified initial change information 200 ₀′, which indicates all the source data as changed. All the source data as of the initial point-in-time is copied to the changed data 120 in the repository 110. The PiT copy 200 ₀′ from the storage controller 100 would be stored as PiT copy information 300 ₀ with a repository offset 308 of zero because the start of the data from the initial PiT copy T₀ is stored at the beginning of the changed data 120 in the repository 110.

The repository copy manager 108 may send (at block 408) a command to the PiT copy manager 116 to create a subsequent PiT copy (T_(i+1)) at a subsequent point-in-time T_(i+1), which would result in PiT copy information 200 _((i+1)). In one embodiment, the repository copy manager 108 may send individual commands to the PiT copy manager 116 to create PiT copies and freeze a previously created PiT copy. In an alternative embodiment, the repository copy manager 108 may send one command to the PiT copy manager 116 to instruct it to periodically create PiT copies of the source data 104, where the creation of a subsequent PiT copy freezes the previously created PiT copy. Still further, the PiT copy manager 116 at the storage controller 100 may be independently creating PiT copies without prompting from the repository copy manager 108.

Upon determining (at block 410) that the previous point-in-time copy at T_(i) completed, the repository copy manager 116 sends (at block 412) to the repository 110 for storage the PiT copy information 200 _(i) for the PiT copy at time T_(i), including the change information 206 _(i) and the changed PiT data 208 _(i) to store in the repository PiT copy information 300 _(i) for T_(i). In one embodiment, a PiT copy at point-in-time T_(i) may be completed upon the creation of the subsequent PiT copy at time T_(i+1). In an alternative embodiment, a PiT copy may be completed by issuing a freeze command to freeze the PiT copy so that the change information 206 stops indicating changes to the source data 104. The repository copy manager 108 creates (at bock 414) in the repository PiT copy information 300, from the received PiT copy information 200 _(i).

The repository copy manager 108 may transmit (at block 416) the source data 104 at the subsequent time (T_(i+1)) that has changed since the previous time to the changed data 120 in the repository 110 to make the full copy current as of the subsequent time T_(i+1). To perform this operation, the repository copy manager 108 may determine from the change information 206 for the previous PiT copy at T_(i) the data units in the source data 104 that have changed and then copy those data units from the source data 104 to the changed data 120. In this way, at the subsequent point-in-time T_(i+1) when the subsequent PiT copy (T_(i+1)) is created, data units in the source data 104 that have changed between the previous point-in-time T_(i) and the subsequent point-in-time T_(i+1) are copied to the changed data 120 in the repository 110.

The repository copy manager 108 may indicate (at block 418) in the repository offset 308 the data unit offset in the changed data 120 where the changed data for the PiT copy at T_(i) begins in the changed data 120. If (at block 420) further point-in-time copies are to be created, then the repository copy manager 108 considers (at block 422) the current subsequent point-in-time copy at (T_(i+1)) to be the previous point-in-time copy at T_(i) during the next iteration of processing the next PiT copy. In this way, i is effectively incremented as the current subsequent point-in-time T_(i+1) becomes the previous point-in-time and a next point-in-time becomes the new subsequent point-in-time. Control then proceeds back to block 408 to create or process a new subsequent PiT copy (T_(i+i)) at a new subsequent point-in-time T_(i+1). If (at block 420) there are no further PiT copies to process, then control ends.

With the described embodiments of FIG. 4, a repository 110 of a full copy of the source data 104 having PiT copy information for different PiT copies is created independently of the storage controller 100 operations to create the PiT copies. In this way, the logic or operations of the repository management operations are independent of the storage controller 100 logic to create PiT copies.

FIGS. 5 a, 5 b, 5 c illustrate examples of the operations of FIG. 4 to copy all the source data at different point-in-times to the changed data 120 and repository PiT copy information 200 b. FIG. 5 a shows the state at an initial time T₀ of the source data 104 ₀ in the source storage 102 that is copied to the changed data 120 ₀ in the repository 110, which may comprise all the source data 104 as of the initial time T₀. Further, a PiT information copy 200 ₀ is created at the initial time T₀ which has change information 206 ₀′ indicating that all the source data has changed at the storage controller 100.

FIG. 5 b shows a time T₁ when a second PiT copy 200 ₁ at T₁ is created, which may result in the completion or freezing of the previous PiT copy 200 ₀ at T₀ having changed data 208 ₀ as of the point-in-time T₀ before changes occurring between T₀ and T₁. The repository copy manager 108 copies the changed data between T₀ and T₁, shown as units 520 and 522, to the changed data 120 ₁ in the repository 110 to update the changed data 120 ₁ to have changed data 520, 522 as of T₁, which follows the initial written data. Further, the completed, or frozen, PiT copy information 200 ₀ at T₀ is copied to the repository 110 to store as repository PiT copy 300 ₀, which includes an offset 308 ₀ indicating zero because the source data for the initial PiT copy 200 ₀ is the first data written to the changed data 120 ₁.

FIG. 5 c shows a time T₂ when a third PiT copy 200 ₂ at T₂ is created, which may result in the completion or freezing of the PiT copy 200 ₁ at T₁ having changed data 208 ₁ as of the point-in-time T₁ before changes occurring between T₁ and T₂. The repository copy manager 108 copies the changed data between T₁ and T₂, shown as 524 and 526, to the repository 110 to update the changed data 120 ₂ to have data as of T₂. Further, the completed, or frozen, PiT copy information 200 ₁ at T₁ is copied to the repository 110 to store as repository PiT copy 300 ₁, which includes a repository offset 308 ₁ indicating the data unit offset in the repository 120 ₂ at which the changed data 520 and 522 begins.

FIG. 6 illustrates an embodiment of operations performed by the repository copy manager 108 to create a restore copy 124 from the repository 110 as of a restore time (T_(R)), which may comprise a point-in-time of one of the repository point-in-time copies 200 _(b). Upon processing (at block 600) a restore request to create a restore copy of the source data as of the restore time (T_(R)), the restore copy manager 108 configures (at block 602) an empty restore copy 124 or restore volume. The restore copy manager 108 may further generate (at block 604) restore copy information 130 for the restore copy having information on the changed data 120 that comprises the data for the restore3 copy 124 as of the restore point-in-time (T_(R)). The empty restore copy 124 is returned (at block 606) to the restore request to make available for access immediately.

FIG. 7 illustrates an embodiment of restore copy information 700 generated at block 604 for a restore copy 124, including a restore copy identifier (ID) 702 identifying the restore copy; a restore point-in-time (T_(R)) 704 the user selected to create the restore copy 124 to which the data from the changed data 120 for the restore is copied; a restore copy location 706 indicating a location in the second storage 112 at which the restore copy 702 is stored; and data unit information 708 providing information for each of the data units in the restore copy 702.

FIG. 8 illustrates an embodiment of an instance of data unit information 708, for data unit i indicating a data unit number 800 of the data unit i, which may comprise an integer number indicating a sequential number of the data unit in the source data 104, e.g., a block number; a copy bit 802 indicating whether the data unit 800 is located in the restore copy 124 or only in the repository 110; and a repository location 804 indicating a location, such as an offset, in the changed data 120 at which the data unit 800 is located in the repository 110. The repository location 804 may comprise an absolute byte location in the changed data 120 or comprise an offset, e.g., block number, from which the byte location can be determined by multiplying the offset times a data unit length. The repository location 804 is used to locate the data unit as of the restore time (T_(R)) from multiple copies of the data unit in the changed data 120 at different point-in-times.

In alternative embodiments, the information used to locate the data units in the changed data 120 may be in different formats, such as indicating the PiT copy from which the data unit 800 is obtained or indicate other offset information that may be used to calculate the specific location in the changed data 120 of the data unit 800.

FIG. 9 illustrates an embodiment of operations performed by the repository copy manager 108 to generate the restore copy information 700, such as the operation performed at block 604 in FIG. 6. Upon initiating the operation (at block 900) to determine the restore copy information 700, the repository copy manager 108 initializes (at block 902) restore copy information 800, such as by indicating the restore point-in-time 704, the restore copy location 706, and the data unit information 708. The copy bit 802 for each data unit 800 may be set to indicate that the data unit is not yet located in the restore copy 124. T_(i) is set (at block 904) to T_(R). The repository copy manager 106 determines (at block 906) the changed data units 120 for the PiT copy 300 _(i) at time T_(i) whose location has not been determined, i.e., do not have a value set for the repository location 804 for the data unit

For each determined changed data unit at step 906, the repository copy manager 106 determines (at block 908) from the repository offset 308, for the PiT copy at Ti the location in the changed data 120 of the data unit. In one embodiment, the repository offset 308 may provide just information for the first changed data unit of the PiT copy and the repository copy manager 108 must determine the offset for a particular data unit based on the number of the changed data unit, i.e., jth changed data unit indicated in the PiT copy change information 306, plus the repository offset 308 _(i), then that sum times a data unit length. Alternatively, the repository offset 308 may indicate the offset number in the changed data 120 for each changed data unit for PiT copies following the initial PiT copy at T₀.

For instance, in an embodiment, where the repository offset 308 i comprises an offset at which the changed data for the PiT copy at Ti begins in the changed data 120, the determined location may comprise the changed data unit number, comprising the number in the order in which the data unit was written for the PiT copy at Ti, plus the repository offset 308 i for the PiT copy at Ti, with this sum multiplied by the data unit length. For instance, if the data unit is the third data unit for the PiT copy at Ti written to the changed data 120 and the data unit number offset at which the changed data for the PiT copy at Ti begins in the change data 120 is 100, and the data unit length is 16 bytes, then the location for the data unit in the changed data 120 comprises the sum of three times 100 multiplied by 16, e.g., (3+100)×16, which equals 4800^(th) byte in the changed data 120. For each determined changed data unit, the repository copy manager 108 indicates (at block 910) the determined location for the data unit in the repository location 804 for the data unit.

If (at block 914) T_(i) equals T₀, then all repository PiT copies 300 at or before the restore time (T_(R)) have been considered, and control ends. Otherwise, if T_(i) does not equal T₀, then T_(i) is set (at block 916) to T_(i−1) to proceed back to block 906 to consider the next PiT copy 300 _(i−1) immediately preceding the last considered PiT copy 300 _(i). With the operations of FIG. 9, changed data units are determined from the repository PiT copies 300 from the PiT copy closest to the restore time in reverse temporal order. In this way, if multiple PiT copies provide changed data for the same source data unit, then the changed data that is indicated for the restore copy being created comes from the PiT copy providing changed data for that data unit that is closest in time to the restore time T_(R) so that the restore copy 124 is provided with changed data 120 from the repository 110 as of the restore time T_(R).

FIG. 10 illustrates an embodiment of operations performed by the restore copy I/O manager 126 to process a write request to the restore copy 124. Upon processing (at block 1000) a write request to the restore copy, the received write data is applied (at block 1002) to the restore copy 124.

FIG. 11 illustrates an embodiment of operations performed by the restore copy I/O manager 126 to process a read request to a requested data unit in the restore copy 124. Upon processing (at block 1100) the read request to a data unit j in the restore copy 124, if (at block 1102) the copy bit 802 _(j) for data unit j indicates that the requested data unit is in the restore copy 124, then the data unit is accessed (at block 1104) from the restore copy 124 and returned to the request. Otherwise, if the request copy 124 does not store the requested data unit as of the restore time (T_(R)), then the restore copy I/O manager 126 determines (at block 1106) from the repository 110 the location in the repository 110 for the changed data for a point-in-time copy having a point-in-time from the restore point-in-time to the initial point-in-time and closest in time to the restore point-in-time (e.g., indicated in the repository offset 308 _(j) for the data unit j). The requested data unit j is accessed (at block 1108) from the determined location in the changed data 120 in the repository 110 to return to the read request. The accessed data unit j may be copied (at block 1110) to the restore copy 124 to make available for future read requests and the copy bit 802 _(j) for data unit j is updated to indicate the data unit is in the restore copy 124. In an alternative embodiment, the accessed data unit may not be copied to the restore copy 124, and instead always returned from the changed data 120 in the repository 110.

With the described embodiments, the restore copy 124 may be generated almost instantaneously because no data needs be copied to the restore copy 124 before it is made available for access. Upon processing read request, the restore copy information 700 may be used to determine whether requested read data from the restore copy 124 is at the restore copy 124 or only in the changed data 120 to determine whether to return the requested data from the restore copy 124 or the changed data 120.

FIG. 12 illustrates an embodiment in which the host 1206 implements a plurality of virtual machines 1230 for which different restore copies 1224 are created for use by the different virtual machines 1230. Elements 1200, 1206, 1208, 1214, 1226, 1210, 1212, 1220, 1224 and 1230 in FIG. 12 are the same as corresponding elements 100, 106, 114, 108, 126, 110, 112, 120, 124, and 300 described with respect to FIG. 1. However, in FIG. 12, the repository copy manager 1208 creates restore copies 1224 for the different virtual machines 1230 to use and the restore copy I/O manager 1226 manages virtual machine 1230 read and write requests to their respective restore copies 1224 as discussed with respect to the restore copy I/O manager 126. In an alternative embodiment, each virtual machine 1230 may include its own instantiation of the repository copy manager 1208 and the restore copy I/O manager 1226. In this way, the different virtual machines 1230 may access their own separate restore copies 1224, and receive data as of the restore point-in-time (T_(R)) from the repository PiT copy information 200 b if needed.

The present invention may be a system, a method, and/or a computer program product. The computer program product may include a computer readable storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device.

Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Java, Smalltalk, C++ or the like, and conventional procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions.

These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks.

The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). In some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.

The computational components of FIG. 1 and FIG. 12, including the storage controller 100, 1200 and host 106, 1206 may be implemented in one or more computer systems, such as the computer system 1302 shown in FIG. 13. Computer system/server 1302 may be described in the general context of computer system executable instructions, such as program modules, being executed by a computer system. Generally, program modules may include routines, programs, objects, components, logic, data structures, and so on that perform particular tasks or implement particular abstract data types. Computer system/server 1302 may be practiced in distributed cloud computing environments where tasks are performed by remote processing devices that are linked through a communications network. In a distributed cloud computing environment, program modules may be located in both local and remote computer system storage media including memory storage devices.

As shown in FIG. 13, the computer system/server 1302 is shown in the form of a general-purpose computing device. The components of computer system/server 1302 may include, but are not limited to, one or more processors or processing units 1304, a system memory 1306, and a bus 1308 that couples various system components including system memory 1306 to processor 1304. Bus 1308 represents one or more of any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, an accelerated graphics port, and a processor or local bus using any of a variety of bus architectures. By way of example, and not limitation, such architectures include Industry Standard Architecture (ISA) bus, Micro Channel Architecture (MCA) bus, Enhanced ISA (EISA) bus, Video Electronics Standards Association (VESA) local bus, and Peripheral Component Interconnects (PCI) bus.

Computer system/server 1302 typically includes a variety of computer system readable media. Such media may be any available media that is accessible by computer system/server 1302, and it includes both volatile and non-volatile media, removable and non-removable media.

System memory 1306 can include computer system readable media in the form of volatile memory, such as random access memory (RAM) 1310 and/or cache memory 1312. Computer system/server 1302 may further include other removable/non-removable, volatile/non-volatile computer system storage media. By way of example only, storage system 1313 can be provided for reading from and writing to a non-removable, non-volatile magnetic media (not shown and typically called a “hard drive”). Although not shown, a magnetic disk drive for reading from and writing to a removable, non-volatile magnetic disk (e.g., a “floppy disk”), and an optical disk drive for reading from or writing to a removable, non-volatile optical disk such as a CD-ROM, DVD-ROM or other optical media can be provided. In such instances, each can be connected to bus 1308 by one or more data media interfaces. As will be further depicted and described below, memory 1306 may include at least one program product having a set (e.g., at least one) of program modules that are configured to carry out the functions of embodiments of the invention.

Program/utility 1314, having a set (at least one) of program modules 1316, may be stored in memory 1306 by way of example, and not limitation, as well as an operating system, one or more application programs, other program modules, and program data. Each of the operating system, one or more application programs, other program modules, and program data or some combination thereof, may include an implementation of a networking environment. The components of the computer 1302 may be implemented as program modules 1316 which generally carry out the functions and/or methodologies of embodiments of the invention as described herein. The systems of FIGS. 1 and 12 may be implemented in one or more computer systems 1302, where if they are implemented in multiple computer systems 1302, then the computer systems may communicate over a network.

Computer system/server 1302 may also communicate with one or more external devices 1318 such as a keyboard, a pointing device, a display 1320, etc.; one or more devices that enable a user to interact with computer system/server 1302; and/or any devices (e.g., network card, modem, etc.) that enable computer system/server 1302 to communicate with one or more other computing devices. Such communication can occur via Input/Output (I/O) interfaces 1322. Still yet, computer system/server 1302 can communicate with one or more networks such as a local area network (LAN), a general wide area network (WAN), and/or a public network (e.g., the Internet) via network adapter 1324. As depicted, network adapter 1324 communicates with the other components of computer system/server 1302 via bus 1308. It should be understood that although not shown, other hardware and/or software components could be used in conjunction with computer system/server 1302. Examples, include, but are not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data archival storage systems, etc.

The terms “an embodiment”, “embodiment”, “embodiments”, “the embodiment”, “the embodiments”, “one or more embodiments”, “some embodiments”, and “one embodiment” mean “one or more (but not all) embodiments of the present invention(s)” unless expressly specified otherwise.

The terms “including”, “comprising”, “having” and variations thereof mean “including but not limited to”, unless expressly specified otherwise.

The enumerated listing of items does not imply that any or all of the items are mutually exclusive, unless expressly specified otherwise.

The terms “a”, “an” and “the” mean “one or more”, unless expressly specified otherwise.

Devices that are in communication with each other need not be in continuous communication with each other, unless expressly specified otherwise. In addition, devices that are in communication with each other may communicate directly or indirectly through one or more intermediaries.

A description of an embodiment with several components in communication with each other does not imply that all such components are required. On the contrary a variety of optional components are described to illustrate the wide variety of possible embodiments of the present invention.

Further, although process steps, method steps, algorithms or the like may be described in a sequential order, such processes, methods and algorithms may be configured to work in alternate orders. In other words, any sequence or order of steps that may be described does not necessarily indicate a requirement that the steps be performed in that order. The steps of processes described herein may be performed in any order practical. Further, some steps may be performed simultaneously.

When a single device or article is described herein, it will be readily apparent that more than one device/article (whether or not they cooperate) may be used in place of a single device/article. Similarly, where more than one device or article is described herein (whether or not they cooperate), it will be readily apparent that a single device/article may be used in place of the more than one device or article or a different number of devices/articles may be used instead of the shown number of devices or programs. The functionality and/or the features of a device may be alternatively embodied by one or more other devices which are not explicitly described as having such functionality/features. Thus, other embodiments of the present invention need not include the device itself.

The illustrated operations of the figures show certain events occurring in a certain order. In alternative embodiments, certain operations may be performed in a different order, modified or removed. Moreover, steps may be added to the above described logic and still conform to the described embodiments. Further, operations described herein may occur sequentially or certain operations may be processed in parallel. Yet further, operations may be performed by a single processing unit or by distributed processing units.

The foregoing description of various embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not by this detailed description, but rather by the claims appended hereto. The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims herein after appended. 

What is claimed is:
 1. A computer program product for maintaining source data in a repository, wherein the computer program product comprises a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause operations, the operations comprising: copying all the source data as of an initial point-in-time to a repository; initiating point-in-time copies at different point-in-times of the source data following the initial point-in-time; in response to completing each of the point-in-time copies, transmitting to the repository change information for the point-in-time copy indicating changed data in the source data that changed between the point-in-time of the point-in-time copy and a subsequent point-in-time; for each point-in-time copy, copying changed source data comprising source data indicated in the change information for the point-in-time copy as changed to the repository; receiving a restore request to restore the source data as of a restore point-in-time; and returning a restore copy to the restore request before the source data in the repository as of the restore point-in-time is copied to the restore copy.
 2. The computer program product of claim 1, wherein the operations further comprise: receiving a read request directed to requested data in the restore copy; determining whether the restore copy includes the requested data; and returning the requested data from the changed data for one of the point-in-time copies in the repository at a point-in-time from the restore point-in-time to the initial point-in-time in the repository in response to determining that the restore copy does not include the requested data.
 3. The computer program product of claim 2, wherein the operations further comprise: copying the returned requested data to the restore copy; and returning the requested data from the restore copy in response to determining that the requested data is in the restore copy.
 4. The computer program product of claim 2, wherein when multiple point-in-time copies in the repository provide changed data for the requested data, the changed data from the point-in-time copy having a point-in-time from the restore point-in-time to the initial point-in-time and closest in time to the restore point-in-time is returned as the requested data.
 5. The computer program product of claim 1, wherein the point-in-time copies are generated by a point-in-time copy program and wherein a repository copy program executed separately from the point-in-time copy program performs the operations of copying to the repository the change information and the changed data at the subsequent point-in-time indicated in the change information as changed.
 6. The computer program product of claim 2, wherein the operations further comprising: indicating for each point-in-time copy in the repository a repository offset for indicating an offset in the repository where the changed data for the point-in-time copy is written.
 7. The computer program product of claim 6, wherein the operations further comprise: generating restore copy information indicating location information used to locate each data unit in the repository at which the source data for the data units in the repository are stored, wherein when multiple point-in-time copies provide changed data as of the restore point-in-time, the location information is determined from the repository offset for the point-in-time copy having a point-in-time from the restore point-in-time to the initial point-in-time and closest in time to the restore point-in-time, wherein returning the requested data from the repository comprises using the location information indicated in the restore copy information for the requested data unit to access the requested data from the repository.
 8. The computer program product of claim 7, wherein the generating the restore copy information comprises: for each point-in-time copy at or before the restore point-in-time, starting from the point-in-time copy closest to the restore time and considering point-in-time copies in reverse time order, performing: determining the changed data units for the point-in-time copy that have not already had location information indicated in the restore copy information; for each of the determined changed data units, using the repository offset for the point-in-time copy to determine a location in the repository at which the determined changed data units are stored; indicating in the restore copy information the determined location in the repository for each of the determined changed data units.
 9. The computer program product of claim 1, wherein the operations further comprise: receiving writes directed to the restore copy; and applying the writes to update the restore copy.
 10. The computer program product of claim 1, wherein multiple of the restore requests are received from multiple virtual machines to create restore copies at different point-in-times, wherein for each of the virtual machines operations are performed comprising: receiving a read request from a requesting virtual machine comprising one of the virtual machines directed to requested data in a restore copy for the requesting virtual machine; returning the requested data from the changed data for one of the point-in-time copies in the repository to the requesting virtual machine.
 11. A system for maintaining source data in a repository, comprising: a processor; and a computer readable storage medium including program instructions executed by the processor to perform operations, the operations comprising: copying all the source data as of an initial point-in-time to a repository; initiating point-in-time copies at different point-in-times of the source data following the initial point-in-time; in response to completing each of the point-in-time copies, transmitting to the repository change information for the point-in-time copy indicating changed data in the source data that changed between the point-in-time of the point-in-time copy and a subsequent point-in-time; for each point-in-time copy, copying changed source data comprising source data indicated in the change information for the point-in-time copy as changed to the repository; receiving a restore request to restore the source data as of a restore point-in-time; and returning a restore copy to the restore request before the source data in the repository as of the restore point-in-time is copied to the restore copy.
 12. The system of claim 11, wherein the operations further comprise: receiving a read request directed to requested data in the restore copy; determining whether the restore copy includes the requested data; and returning the requested data from the changed data for one of the point-in-time copies in the repository at a point-in-time from the restore point-in-time to the initial point-in-time in the repository in response to determining that the restore copy does not include the requested data.
 13. The system of claim 12, wherein when multiple point-in-time copies in the repository provide changed data for the requested data, the changed data from the point-in-time copy having a point-in-time from the restore point-in-time to the initial point-in-time and closest in time to the restore point-in-time is returned as the requested data.
 14. The system of claim 12, wherein the operations further comprising: indicating for each point-in-time copy in the repository a repository offset for indicating an offset in the repository where the changed data for the point-in-time copy is written.
 15. The system of claim 14, wherein the operations further comprise: generating restore copy information indicating location information used to locate each data unit in the repository at which the source data for the data units in the repository are stored, wherein when multiple point-in-time copies provide changed data as of the restore point-in-time, the location information is determined from the repository offset for the point-in-time copy having a point-in-time from the restore point-in-time to the initial point-in-time and closest in time to the restore point-in-time, wherein returning the requested data from the repository comprises using the location information indicated in the restore copy information for the requested data unit to access the requested data from the repository.
 16. The system of claim 15, wherein the generating the restore copy information comprises: for each point-in-time copy at or before the restore point-in-time, starting from the point-in-time copy closest to the restore time and considering point-in-time copies in reverse time order, performing: determining the changed data units for the point-in-time copy that have not already had location information indicated in the restore copy information; for each of the determined changed data units, using the repository offset for the point-in-time copy to determine a location in the repository at which the determined changed data units are stored; indicating in the restore copy information the determined location in the repository for each of the determined changed data units.
 17. The system of claim 11, wherein multiple of the restore requests are received from multiple virtual machines to create restore copies at different point-in-times, wherein for each of the virtual machines operations are performed comprising: receiving a read request from a requesting virtual machine comprising one of the virtual machines directed to requested data in a restore copy for the requesting virtual machine; returning the requested data from the changed data for one of the point-in-time copies in the repository to the requesting virtual machine.
 18. A method, comprising: copying source data as of an initial point-in-time to a repository; initiating point-in-time copies at different point-in-times of the source data following the initial point-in-time; in response to completing each of the point-in-time copies, transmitting to the repository change information for the point-in-time copy indicating changed data in the source data that changed between the point-in-time of the point-in-time copy and a subsequent point-in-time; for each point-in-time copy, copying changed source data comprising source data indicated in the change information for the point-in-time copy as changed to the repository; receiving a restore request to restore the source data as of a restore point-in-time; and returning a restore copy to the restore request before the source data in the repository as of the restore point-in-time is copied to the restore copy.
 19. The method of claim 18, further comprising: receiving a read request directed to requested data in the restore copy; determining whether the restore copy includes the requested data; and returning the requested data from the changed data for one of the point-in-time copies in the repository at a point-in-time from the restore point-in-time to the initial point-in-time in the repository in response to determining that the restore copy does not include the requested data.
 20. The method of claim 19, wherein when multiple point-in-time copies in the repository provide changed data for the requested data, the changed data from the point-in-time copy having a point-in-time from the restore point-in-time to the initial point-in-time and closest in time to the restore point-in-time is returned as the requested data.
 21. The method of claim 19, further comprising: indicating for each point-in-time copy in the repository a repository offset for indicating an offset in the repository where the changed data for the point-in-time copy is written.
 22. The method of claim 21, further comprising: generating restore copy information indicating location information used to locate each data unit in the repository at which the source data for the data units in the repository are stored, wherein when multiple point-in-time copies provide changed data as of the restore point-in-time, the location information is determined from the repository offset for the point-in-time copy having a point-in-time from the restore point-in-time to the initial point-in-time and closest in time to the restore point-in-time, wherein returning the requested data from the repository comprises using the location information indicated in the restore copy information for the requested data unit to access the requested data from the repository.
 23. The method of claim 22, wherein the generating the restore copy information comprises: for each point-in-time copy at or before the restore point-in-time, starting from the point-in-time copy closest to the restore time and considering point-in-time copies in reverse time order, performing: determining the changed data units for the point-in-time copy that have not already had location information indicated in the restore copy information; for each of the determined changed data units, using the repository offset for the point-in-time copy to determine a location in the repository at which the determined changed data units are stored; indicating in the restore copy information the determined location in the repository for each of the determined changed data units.
 24. The method of claim 18, wherein multiple of the restore requests are received from multiple virtual machines to create restore copies at different point-in-times, wherein for each of the virtual machines operations are performed comprising: receiving a read request from a requesting virtual machine comprising one of the virtual machines directed to requested data in a restore copy for the requesting virtual machine; returning the requested data from the changed data for one of the point-in-time copies in the repository to the requesting virtual machine. 